A new study from researchers at the University of California at San Diego and Los Angeles suggests that a sharp uptick in fatal medication mistakes in July corresponds with the entry of thousands of trainee doctors into medical residency programs across the U.S.

Around 1.5 million preventable medication errors occur in the American health system each year at a cost of over $4 billion annually, according to a new report released yesterday by the Food and Drug Administration (FDA). The report’s release marks the start of a new effort to reduce those numbers.